The invention relates to a device for producing a perforation track in an advancing web, e.g. a paper web, by comb teeth piercing the web.
A preferred use for this device is in a winding machines, in which a web is wound up to form a reel. For performing a reel change, a perforation track running transverse to the web running direction is produced in the web by the device. Following this, the web is severed along the perforation track.
Perforation track forming devices are disclosed in:
(1) DE 36 11 895 C2 PA1 (2) DE 40 34 997 C1 PA1 (3) DE OS 1 938 234
Known devices for perforating a running paper web have disadvantages. The perforation device according to FIG. 2 in document (1) has a shaft with a comb which cooperates with a mating roll having a resilient cover. When the perforation device is not operating, the perforation comb is located at a position in which it does not contact the paper web. To lay a perforation track in the paper web, the shaft makes one revolution. The perforation comb is thereby moved into and then out of the paper web and it leaves a perforation track. This device has the disadvantage that its construction is very complex. Its control means must operate very precisely because the shaft and the mating roll must run in synchronism with the paper web. Otherwise, premature severing of the web results.
In the embodiment of FIG. 1 in document (1), the shaft runs in the opposite direction to the paper web. This leads to an undefined perforation and to the risk of a web break during the perforation process.
Document (2) discloses a device for severing a paper web. In this case, while the machine (e.g. the winding machine) is stationary, pressure is applied to the web which is resting on a supporting roll, in order to crush the web and hence to weaken it. The web is then completely severed by increasing the web tension. This device has the disadvantage that the winding machine must be stopped for the purpose of weakening the web. As a result, the reel change process takes a relatively long time. In addition, there is a risk of damage to the surface of the supporting roll.
Document (3) shows a supported web being pierced by comb teeth, but does show a support not for piercing transversely across a web, which is the problem with which the invention is concerned.